WTPS21 PGTW 042100 MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/TROPICAL CYCLONE FORMATION ALERT (INVEST 90P)// RMKS/ 1. FORMATION OF A SIGNIFICANT TROPICAL CYCLONE IS POSSIBLE WITHIN 140 NM EITHER SIDE OF A LINE FROM 12.6S 151.7W TO 19.6S 144.8W WITHIN THE NEXT 12 TO 24 HOURS. AVAILABLE DATA DOES NOT JUSTIFY ISSUANCE OF NUMBERED TROPICAL CYCLONE WARNINGS AT THIS TIME. WINDS IN THE AREA ARE ESTIMATED TO BE 28 TO 33 KNOTS. METSAT IMAGERY AT 041800Z INDICATES THAT A CIRCULATION CENTER IS LOCATED NEAR 12.8S 151.4W. THE SYSTEM IS MOVING EAST-SOUTHEASTWARD AT 14 KNOTS. 2. REMARKS: THE AREA OF CONVECTION (INVEST 90P) PREVIOUSLY LOCATED NEAR 12.5S 152.8W IS NOW LOCATED NEAR 12.8S 151.4W, APPROXIMATELY 225 NM NORTH OF BORA BORA. MULTISPECTRAL SATELLITE IMAGERY REVEALS A COMPACT AND MOSTLY OBSCURED LOW LEVEL CIRCULATION CENTER (LLCC), WHICH HAS RAPIDLY CONSOLIDATED OVER THE LAST 12 HOURS. CONVECTION IS FLARING OVER THE EASTERN SEMICIRCLE, DEVELOPING INTO NASCENT BANDING FEATURES AND WRAPPING INTO THE CENTER. A 041156Z NOAA-20 ATMS 89GHZ MICROWAVE IMAGE DEPICTED A SMALL REGION OF CENTRAL CONVECTION AND A SHALLOW BANDING FEATURE TO THE NORTH AND SOUTH, BEGINNING TO WRAP INWARD TOWARDS THE DEVELOPING LLCC. ENVIRONMENTAL ANALYSIS SHOWS A FAVORABLE ENVIRONMENT FOR ANALYSIS WITH MODERATE UPPER LEVEL POLEWARD OUTFLOW, LOW VERTICAL WIND SHEAR OF 10-15 KTS, AND SEA SURFACE TEMPERATURES OF 28 TO 29 C. GLOBAL MODELS ARE IN AGREEMENT THAT 90P WILL TRACK RAPIDLY SOUTH- SOUTHEASTWARD IN THE WAKE OF 99P OVER THE NEXT COUPLE OF DAYS WHILE QUICKLY CONSOLIDATING AND INTENSIFYING. ANALYSIS SHOWS 90P TO BE TROPICAL IN NATURE AND IT IS EXPECTED TO REMAIN SO FOR AT LEAST THE NEXT 48 HOURS. MODELS AGREE THAT 90P WILL QUICKLY CONSOLIDATE AND INTENSIFY OVER THE NEXT 24 HOURS AS IT TRACKS NORTH OF TAHITI. MAXIMUM SUSTAINED SURFACE WINDS ARE ESTIMATED AT 28 TO 33 KNOTS. MINIMUM SEA LEVEL PRESSURE IS ESTIMATED TO BE NEAR 1004 MB. THE POTENTIAL FOR THE DEVELOPMENT OF A SIGNIFICANT TROPICAL CYCLONE WITHIN THE NEXT 24 HOURS IS HIGH. MAXIMUM SUSTAINED SURFACE WINDS ARE ESTIMATED AT 28 TO 33 KNOTS. MINIMUM SEA LEVEL PRESSURE IS ESTIMATED TO BE NEAR 998 MB. THE POTENTIAL FOR THE DEVELOPMENT OF A SIGNIFICANT TROPICAL CYCLONE WITHIN THE NEXT 24 HOURS IS HIGH. 3. THIS ALERT WILL BE REISSUED, UPGRADED TO WARNING OR CANCELLED BY 052100Z.// NNNN